1. Field of the Invention
The present invention relates to a multi-cylinder refrigerant gas compressor preferably adapted for use in an automobile air-conditioning system, more specifically, it relates to a swash plate type compressor with a muffling arrangement for suppressing discharge pressure pulsation in a refrigerant gas after compression.
2. Description of the Related Art
In a multi-cylinder refrigerant gas compressor for use in an automobile air-conditioning system, refrigerant gas returning from the air-conditioning system is pumped into and compressed by a multi-cylinder compressing system having pistons operated by an actuator, such as a rotary swash plate. The refrigerant gas, when compressed, is discharged from the cylinder bores into discharge chambers provided axially at front and/or rear sides of a cylinder block unit of the compressor. The compressed refrigerant gas is then passed through discharge passageways of the cylinder block unit and the separate flows of the gas collected together. Subsequently, the collected refrigerant gas is sent through a connecting flange element toward a cooling circuit of the air-conditioning system.
During the above-mentioned compressing and discharging of the refrigerant gas, pulsation occurs in the discharge pressure of the gas due to the reciprocating motion of the pistons, the frequency of the pulsation depending on the number of cylinder bores, and this pulsation must be suppressed to prevent noise and vibration problems. Accordingly, a muffling chamber has conventionally been provided in the refrigerant-gas delivery circuit for reducing the pulsation in the discharge pressure of the refrigerant gas.
U.S. Pat. No. 4,610,604 to Iwamori discloses a multi-cylinder swash plate type compressor having a connecting flange which defines therein a muffling chamber and a collision zone. In the compressor, the refrigerant gas compressed by the swash-plate operated piston mechanism is delivered from a front and a rear discharge chamber as a pair of opposed streams of the compressed refrigerant gas into the collision zone, wherein the opposed streams of refrigerant gas are allowed to directly collide to thereby weaken the pulsation in the discharge pressure of the compressed refrigerant gas. The refrigerant gas is then sent to the muffling chamber to completely suppress the pulsation, and subsequently delivered to the cooling circuit via the connecting flange. However, in the collision zone of the compressor of U.S. Pat. No. 4,610,604, since the opposed streams of the compressed gas are delivered from a pair of coaxially opposed orifices into the collision zone, one of the opposed streams of the compressed refrigerant gas tends to prevent a smooth delivery of the other of the opposed streams of the compressed refrigerant gas from the corresponding orifice. That is, one of the opposed streams of the compressed gas exerts a resistance to the other stream, and therefore, a loss of delivery of the compressed refrigerant gas occurs while the compressed gas flows through the collision zone. The loss of delivery of the compressed refrigerant gas is relatively small in the low and medium rotation speed ranges of the compressor, but becomes large in the high rotation speed range of the compressor, and thus causes noise.